Europe - Seasonal influenza 2018 - 2019 - ECDC-WHO

[Gert van der Hoek]

Weeks 52/2018 (24–30 December 2018)

• Influenza activity continued to increase in the European Region. Of the individuals sampled after presenting with ILI or ARI to sentinel primary healthcare sites, 37% tested positive for influenza viruses.
• The majority of influenza virus detections were type A in both inpatients and outpatients.
• From sentinel samples, influenza A(H3N2) and A(H1N1)pdm09 viruses were detected in similar proportions.
• From non-sentinel samples, about two third of the A viruses were A(H1N1)pdm09.
• Most of the hospitalized laboratory confirmed influenza infections were associated with A(H1N1)pdm09 virus and were in persons aged 15-64 years.
• The predominant A(H1N1)pdm09 and A(H3N2) viruses that are circulating match the vaccine components, although fewer than 50 A(H3N2) viruses have been genetically characterized and only 13 have been antigenically characterized so far.
• Data from the 13 Member States and areas reporting to the EuroMOMO project indicated all-cause mortality was at expected levels for this time of year.

2018/19 season overview

• Influenza activity in Europe is increasing, with both A viruses circulating widely. Countries should continue to encourage vaccination.
• The northern hemisphere Vaccine Composition Meeting for 2019–2020 has been planned for 18–20 February 2019 in Beijing, China. For more information see here.
  
  

[Gert van der Hoek]

Week 1/2019 (31 December 2018–6 January 2019)

• Influenza activity continued to increase in the European Region. Of the individuals sampled after presenting with ILI or ARI to sentinel primary health care sites, 44.6% tested positive for influenza viruses.
• The majority of influenza virus detections were type A in both inpatients and outpatients.
• Both influenza A(H3N2) and A(H1N1)pdm09 viruses were detected.
• Data from the 21 Member States and areas reporting to the EuroMOMO project indicated all-cause mortality was at expected levels for this time of year.

2018/19 season overview

• Influenza activity in Europe is increasing, with both subtypes of type A viruses circulating widely. Countries should continue to encourage vaccination.
• Most of the hospitalized laboratory confirmed influenza infections were associated with A(H1N1)pdm09 virus and were in persons aged 15-64 years.
• The predominant A(H1N1)pdm09 and A(H3N2) viruses circulating match the vaccine components, although relatively low numbers of influenza A(H3N2) viruses have been characterized and concerns related to egg-adaptation of the virus during production persist, as in previous years.

[Gert van der Hoek]

Week 2/2019 (7?13 January 2019)

• Influenza activity continued to increase in the European Region. Samples collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza-positivity rate of 42.2%.
• Influenza type A virus detections dominated with A(H1N1)pdm09 viruses being slightly more prevalent than A(H3N2). Very few influenza B viruses were detected.
• Data from the 23 Member States and areas reporting to the EuroMOMO project indicated that all-cause mortality was at expected levels for this time of year, but with a few countries starting to observe some excess mortality in elderly populations.

2018/19 season overview

• Influenza activity in Europe is increasing, with both subtypes of influenza A viruses circulating widely. Countries should continue to encourage vaccination. In addition, countries are encouraged to use antivirals in accordance with national guidelines.
• The influenza A(H1N1)pdm09 viruses that have been characterized are antigenically similar to the 2018?2019 northern hemisphere influenza vaccine virus. Fewer influenza A(H3N2) viruses have been antigenically characterized. The effectiveness of vaccines in the population will be evaluated by vaccine effectiveness studies when data becomes available later in the season.
  
  

[Gert van der Hoek]

Week 3/2019 (14-20 January 2019)

• Influenza activity continued to increase in the European Region. Samples collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza positivity rate of 48.8%.
• Influenza type A virus detections dominated with A(H1N1)pdm09 viruses being more prevalent than A(H3N2). Very few influenza B viruses were detected.
• Data from the 23 Member States and areas reporting to the EuroMOMO project indicated that generally all-cause mortality was at expected levels for this time of year, but a few countries observed some excess mortality in elderly populations.
• In Sweden, a seasonal reassortant A(H1N2) influenza virus was detected in a specimen collected at the end of December from an adult. Preliminary whole genome sequence analysis suggests that the virus is a seasonal reassortant containing HA and NS, NP, PA, PB1 and PB2 genes of human seasonal A(H1N1)pdm09 influenza virus and NA genes of human seasonal A(H3N2) influenza virus. No increase in virulence is expected compared to seasonal influenza strains. Further analysis is being conducted by the WHO Collaborating Center on influenza. More information can be found here.

2018/19 season overview

• Influenza activity in Europe is increasing, with both subtypes of influenza A viruses circulating widely. Countries should continue to encourage vaccination. In addition, countries are encouraged to use antivirals in accordance with national guidelines.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary results from Canada where the predominate circulating viruses are influenza A(H1N1)pdm09 viruses, indicate good vaccine effectiveness.

[Gert van der Hoek]

Week 4/2019 (21-27 January 2019)

• Influenza activity continued to increase in the European Region. Samples collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza positivity rate of 51.3%.

• Influenza type A virus detections dominated with A(H1N1)pdm09 viruses and A(H3N2) viruses co-circulating. Very few influenza B viruses were detected.

• Pooled data from 23 Member States and areas reporting to the EuroMOMO project indicated excess mortality in adults and elderly populations overall. However, this result was driven by data from only a few countries.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018 and has increased continuously into week 4/2019. Both subtypes of influenza A viruses are circulating widely, with either A(H1N1)pdm09 or A(H3N2) dominating in some countries, and co-circulation of the two viruses in other countries. Countries should continue to promote vaccination. In addition, countries are encouraged to use antivirals in accordance with national guidelines.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary results from Canada where the predominate circulating viruses are influenza A(H1N1)pdm09 viruses, indicate good vaccine effectiveness. These results are supported by recent preliminary vaccine effectiveness results from Hong Kong, where the vaccine was very effective at preventing A(H1N1)pdm09 related hospitalizations in children.
  

[Gert van der Hoek]

Week 5/2019 (28 January-3 February 2019)

• Influenza activity is widespread in the European Region and continues to increase. Samples collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza positivity rate of 54.7%.

• Influenza type A virus detections dominated with A(H1N1)pdm09 viruses and A(H3N2) viruses co-circulating. Very few influenza B viruses were detected.
• Over 50% of specimens from patients hospitalized with severe acute respiratory infection (SARI) collected in week 5/2019 were positive for influenza, and >99% were type A.

• Pooled data from 22 Member States and areas reporting to the EuroMOMO project indicated excess mortality in a elderly populations overall. However, this result was driven by data from only a few countries.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018 and has increased continuously into week 5/2019, but may be levelling off. The positivity rate has exceeded 50% since week 3/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses. Countries should continue to promote vaccination. In addition, countries are encouraged to use antivirals in accordance with national guidelines.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 76% of influenza A virus detections were subtyped; of these 78% were A(H1N1)pdm09 virus. Among influenza virus-infected patients admitted to other wards, 26% of influenza A virus detections were subtyped and 70% were A(H1N1)pdm09 virus.
• Over 90% of influenza A virus positive cases detected from SARI surveillance since week 40/2018 were subtyped and 82% were A(H1N1)pdm09 virus.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary results from Canada where the predominate circulating viruses are influenza A(H1N1)pdm09 viruses, indicate good vaccine effectiveness. These results are supported by recent preliminary vaccine effectiveness results from Hong Kong, where the vaccine was very effective at preventing A(H1N1)pdm09 related hospitalizations in children.
• Thehigh vaccine effectiveness against A(H1N1)pdm09 viruses is consistent with genetic characterization reports indicating that all circulating viruses belong to clade 6B.1 and remain antigenically similar to the vaccine virus, despite the emergence of a number of subgroups. The lower vaccine effectiveness against A(H3N2) viruses likely reflects the circulation of multiple genetic clades some of which contain viruses that display low antigenic similarity to the vaccine virus, particularly with egg-propagated vaccine virus as compared to cell culture-propagated vaccine virus.

[Gert van der Hoek]

Week 6/2019 (4 -10 February 2019)

• Influenza activity is widespread in the European Region. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 53%, slightly lower than in the previous week (58%).
• Influenza type A virus detections dominated with A(H1N1)pdm09 viruses and A(H3N2) viruses co-circulating. Very few influenza B viruses were detected.
• 46% of specimens from patients hospitalized with severe acute repiratory infection (SARI) collected in week 6/2019 were positive for influenza virus, and all were type A.
• Pooled data from 24 Member States and areas reporting to the EuroMOMO project indicated excess mortality mostly among elderly aged 65 years and above, but also in adults in the age group of 15-64 years.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018 and has increased continuously into week 5/2019 after which it started to decrease. The positivity rate has exceeded 50% since week 3/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 40% of influenza A viruses were subtyped; of these 78% were A(H1N1)pdm09 virus. Among influenza virus-infected patients admitted to other wards, 28% of influenza A viruses were subtyped and 71% were A(H1N1)pdm09 virus.
• Over 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 81% were A(H1N1)pdm09 virus.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses and preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggests the vaccine are effective and estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes (e.g., higher VE in children). See data from Canada, Finland, Hong Kong, Sweden, and the United States.
• Circulating viruses remain susceptible to neuraminidase inhibitors supporting early initiation of treatment and prophylactic use according to national guidelines.
  

[Gert van der Hoek]

Week 7/2019 (11–17 February 2019)

• Influenza activity is widespread in the European Region. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 53%.
• Influenza type A virus detections dominated with slightly more A(H1N1)pdm09 viruses than A(H3N2). Very few influenza B viruses were detected.
• 36% of specimens from patients hospitalized with severe acute repiratory infection (SARI) collected in week 7/2019 were positive for influenza virus, and almost all were type A.
  of specimens from patients hospitalized with severe acute repiratory infection (SARI) collected in week 6/2019 were positive for influenza virus, and all were type A.
• Pooled data from 22 Member States and areas reporting to the EuroMOMO project indicated excess mortality mostly among elderly people aged 65 years and above, but also in adults in the age group of 15-64 years.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018 and has exceeded 50% since week 3/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 37% of influenza A viruses were subtyped; of these 76.2% were A(H1N1)pdm09 virus. Among influenza virus-infected patients admitted to other wards, 31% of influenza A viruses were subtyped and 70% were A(H1N1)pdm09 virus.
• Over 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 81.4% were A(H1N1)pdm09 virus.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggest the vaccines are effective, but estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes. See data from six European studies, Canada, Finland, Hong Kong, Sweden, and the United States.
• On 21 February 2019, WHO published the recommendations for the 2019–2020 northern hemisphere seasonal influenza vaccine composition.
• Circulating viruses remain susceptible to neuraminidase inhibitors supporting early initiation of treatment and prophylactic use according to national guidelines.

[Gert van der Hoek]

Week 8/2019 (18?24 February 2019)

• Influenza activity is widespread in the European Region. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 49%.
• Influenza type A virus detections dominated with slightly more A(H1N1)pdm09 than A(H3N2) viruses. Very few influenza B viruses were detected.
• 41% of specimens from patients with severe acute respiratory infection (SARI) in week 8/2019 were positive for influenza virus, and almost all were type A.
• Pooled data from 21 Member States and areas reporting to the EuroMOMO project indicated excess mortality among persons aged 15?64 years and 65 years and older.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018, exceeded 50% between weeks 3/2019 and 7/2019, and peaked in week 5/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 37% of influenza A viruses were subtyped; of these 68% were A(H1N1)pdm09 viruses. Among influenza virus-infected patients admitted to other wards, 32% of influenza A viruses were subtyped and 68% were A(H1N1)pdm09 viruses.
• Over 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 81% were A(H1N1)pdm09 viruses.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggest the vaccines are effective, but estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes. See data from six European studies, Canada, Finland, Hong Kong, Sweden, and the United States.
• On 21 February 2019, WHO published the recommendations for the influenza vaccine composition to be used in the 2019?2020 northern hemisphere season. The recommendation for B strains remained unchanged, for A(H1N1)pdm09 it was updated, and for A(H3N2) it was postponed to 21 March 2019.
• Circulating viruses remain susceptible to neuraminidase inhibitors supporting early initiation of treatment and prophylactic use according to national guidelines.
  
  
  

[Gert van der Hoek]

Week 9/2019 (25 February-3 March 2019)

• Influenza activity was widespread in the European Region. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 41.8%.
• Influenza type A virus detections dominated with slightly more A(H1N1)pdm09 than A(H3N2) viruses. Very few influenza B viruses were detected.
• 27.4% of specimens from patients with severe acute respiratory infection (SARI) in week 9/2019 tested positive for influenza virus, and almost all were type A.
• Pooled data from 23 Member States and areas reporting to the EuroMOMO project indicated that the excess mortality observed in previous weeks is now declining. Excess mortality was seen in persons aged 65 years and above, and to a lesser extent in persons 15-64 years.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018, exceeded 50% between weeks 3/2019 and 7/2019, and peaked in week 5/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 38% of influenza A viruses were subtyped; of these 73% were A(H1N1)pdm09 viruses. Among influenza virus-infected patients admitted to other wards, 34% of influenza A viruses were subtyped and 65% were A(H1N1)pdm09 viruses.
• Over 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 81% were A(H1N1)pdm09 viruses.
• A recent summary of regional activity from October 2018 to February 2019 was published in Eurosurveillance and can be found here.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggest the vaccines are effective, but estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes. See data from six European studies, Canada, Finland, Hong Kong, Sweden, and the United States.
• On 21 February 2019, WHO published the recommendations for the influenza vaccine composition to be used in the 2019?2020 northern hemisphere season. The recommendation for type B lineages was unchanged, for A(H1N1)pdm09 it was updated, and for A(H3N2) the decision was postponed until 21 March 2019.
• Circulating viruses remain susceptible to neuraminidase inhibitors supporting early use of antiviral treatment according to national guidelines.
  
  
  

[Gert van der Hoek]

Week 10/2019 (4-10 March 2019)

• Influenza activity was widespread in the European Region. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 42.8%.
• Influenza type A virus detections dominated with slightly more A(H1N1)pdm09 than A(H3N2) viruses. Very few influenza B viruses were detected.
• 28.3% of specimens from patients with severe acute respiratory infection (SARI) collected in week 10/2019 tested positive for influenza virus, and almost all were type A.
• Pooled data from 22 Member States and areas reporting to the EuroMOMO project indicated that the excess mortality observed in previous weeks continued to decline. Excess mortality was seen in persons aged 65 years and above and, to a lesser extent, in persons 15-64 years.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018, exceeded 50% between weeks 3/2019 and 7/2019, and peaked in week 5/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 41% of influenza A viruses were subtyped; of these 72% were A(H1N1)pdm09 viruses. Among influenza virus-infected patients admitted to other wards, 35% of influenza A viruses were subtyped and 63% were A(H1N1)pdm09 viruses.
• Over 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 81% were A(H1N1)pdm09 viruses.
• In general, current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggest the vaccines are effective, but estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes. See data from a European study (six countries), Canada, Finland, Hong Kong, Sweden, and the United States.
• On 21 February 2019, WHO published the recommendations for the influenza vaccine composition to be used in the 2019?2020 northern hemisphere season. The recommendation for type B lineages was unchanged, for A(H1N1)pdm09 it was updated, and for A(H3N2) the decision was postponed until 21 March 2019.
• A recent summary of regional activity from October 2018 to February 2019 was published in Eurosurveillance and can be found here.
• Circulating viruses remain susceptible to neuraminidase inhibitors supporting use of antiviral treatment according to national guidelines.

[Gert van der Hoek]

Week 11/2019 (11-17 March 2019)

• Influenza activity was widespread in one-third of the countries of the European Region. Widespread activity was located in northern, southern, and western areas of the European Region. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 34%, a decrease compared to 43% during the previous week.

• Influenza type A virus detections dominated with slightly more A(H1N1)pdm09 than A(H3N2) viruses. Very few influenza B viruses were detected.

• Of the specimens from patients with severe acute respiratory infection (SARI) collected in week 11/2019 that were tested for influenza viruses, 31% were positive and almost all were type A.

• Pooled data from 24 Member States and areas reporting to the EuroMOMO project indicated that the excess mortality observed in previous weeks continued to decline. Excess mortality was seen in persons aged 65 years and in persons 15-64 years.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018, exceeded 50% between weeks 3/2019 and 7/2019, and peaked in week 5/2019.
• Both influenza A virus subtypes are circulating widely, with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 41% of influenza A viruses were subtyped; of these 71% were A(H1N1)pdm09 viruses. Among influenza virus-infected patients admitted to other wards, 37% of influenza A viruses were subtyped and 61% were A(H1N1)pdm09 viruses.
• Over 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 80% were A(H1N1)pdm09 viruses.
• Current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggest the vaccines are effective, but estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes. See data from a European study (six countries), Canada, Finland, Hong Kong, Sweden, and the United States.
• A recent summary of regional activity from October 2018 to February 2019 was published in Eurosurveillance and can be found here.
• WHO has published the recommendations for the composition of influenza vaccines to be used in the 2019?2020 northern hemisphere season. The recommendation was that type B lineages remain unchanged, and the A(H1N1)pdm09 and A(H3N2) strains were updated.
• Circulating viruses remain susceptible to neuraminidase inhibitors supporting use of antiviral treatment according to national guidelines.

[Gert van der Hoek]

Week 12/2019 (18-24 March 2019)

• Of 45 countries reporting on geographic spread only 11, located in northern, southern, and western areas of the European Region, reported widespread activity. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 38%, similar to the rate of 39% in the previous week.

• Of 45 countries reporting on intensity, 41 reported baseline or low intensity. No countries reported high intensity levels.

• Influenza type A virus detections dominated with more A(H3N2) than A(H1N1)pdm09 viruses among sentinel and non-sentinel source specimens. Few influenza B viruses were detected.

• Of the specimens from patients with severe acute respiratory infection (SARI) collected in week 12/2019 that were tested for influenza viruses, 21% were positive and almost all were type A.

• Pooled data from 22 Member States and areas reporting to the EuroMOMO project indicated that the excess mortality observed in previous weeks has returned to normal levels.

2018/19 season overview

• Influenza activity in the European region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018, exceeded 50% between weeks 3/2019 and 7/2019, and peaked in week 5/2019.
• Both influenza A virus subtypes were circulating , with co-circulation in some countries while others report dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 41% of influenza A viruses were subtyped; of these 71% were A(H1N1)pdm09 viruses. Among influenza virus-infected patients admitted to other wards, 37% of influenza A viruses were subtyped and 60% were A(H1N1)pdm09 viruses.
• 90% of influenza A viruses detected from SARI surveillance since week 40/2018 were subtyped and 80% were A(H1N1)pdm09 viruses.
• Current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. Preliminary vaccine effectiveness estimates continue to support the use of vaccines. Early data suggest the vaccines are moderately effective, but estimates vary depending on the population studied and the proportions of circulating influenza A virus subtypes. See data from a European study (six countries), Canada, Finland, Hong Kong (China), Sweden, and the United States of America.
• A recent summary of regional activity from October 2018 to February 2019 was published in Eurosurveillance and can be found here.
• WHO has published the recommendations for the composition of influenza vaccines to be used in the 2019?2020 northern hemisphere season. The recommendation was that type B lineages remain unchanged, and the A(H1N1)pdm09 and A(H3N2) strains were updated.
• Circulating viruses in the European Region remain susceptible to neuraminidase inhibitors supporting use of antiviral treatment according to national guidelines.

• In the United States of America, influenza viruses continue to circulate with an increasing proportion of influenza A(H3N2) viruses. On 28 March 2019, the U.S. Centers for Disease Control and Prevention issued a health advisory reminding U.S. clinicians that A(H3N2) virus infections in older adults may be associated with severe disease and early antiviral treatment is recommended for hospitalized and high-risk patients, especially those aged 65 years and older.

[Gert van der Hoek]

Week 13/2019 (25-31 March 2019)

• Of 45 countries reporting on geographic spread, 11, located in northern, southern, and western areas of the European Region, reported widespread activity. Specimens collected from individuals presenting with ILI or ARI to sentinel primary health care sites yielded an influenza virus positivity rate of 32%, a decrease for the third week in a row.

• Of 45 countries reporting on influenza activity, 42 reported baseline or low intensity levels and none reported high intensity.

• Influenza type A virus detections dominated with more A(H3N2) than A(H1N1)pdm09 viruses among sentinel and non-sentinel source specimens. Very few influenza B viruses were detected.

• Of the specimens from patients with severe acute respiratory infection (SARI) collected in week 13/2019 that were tested for influenza viruses, 33% were positive and all viruses were type A.

• Pooled data from 22 Member States and areas reporting to the EuroMOMO project indicated that the excess mortality observed in previous weeks has returned to normal levels.

2018/19 season overview

• Influenza activity in the European Region, based on sentinel sampling, exceeded a positivity rate of 10% in week 49/2018, exceeded 50% between weeks 3/2019 and 7/2019, and peaked in week 5/2019..
• Both influenza A virus subtypes have circulated, with co-circulation in some countries while others reported dominance of either A(H1N1)pdm09 or A(H3N2) viruses.
• Among hospitalized influenza virus-infected patients admitted to ICU wards, 99% were infected with type A viruses, and of those subtyped, 69% were A(H1N1)pdm09. Among influenza virus-infected patients admitted to other wards, 99% were infected with type A viruses, with 58% of those subtyped being A(H1N1)pdm09.
• Of the patient specimens from SARI surveillance that tested positive for influenza, 99% were infected with influenza type A virus, with 80% of those subtyped being A(H1N1)pdm09.
• A recent summary of regional activity from October 2018 to February 2019 was published in Eurosurveillance and can be found here.
• Current influenza vaccines tend to work better against influenza A(H1N1)pdm09 and influenza B viruses than against influenza A(H3N2) viruses. For more detail, see the Vaccine effectiveness section

• WHO has published recommendations for the composition of influenza vaccines to be used in the 2019?2020 northern hemisphere season. The recommendation was that type B lineage viruses remain unchanged, while the A(H1N1)pdm09 and A(H3N2) viruses were updated.
• Circulating viruses in the European Region remained susceptible to neuraminidase inhibitors supporting use of antiviral treatment according to national guidelines.